package main

import (
	"bufio"
	"fmt"
	"os"
	"time"
)

func main() {
	start := time.Now()
	partOne()
	duration := time.Since(start)
	fmt.Printf("p1: %s\n", duration)
}

func makeScanner(test bool) *bufio.Scanner {
	var f *os.File
	if test {
		f, _ = os.Open("inputs/testinput")
	} else {
		f, _ = os.Open("inputs/input")
	}
	reader := bufio.NewReader(f)
	return bufio.NewScanner(reader)
}

type coord struct {
	x int
	y int
}

type floor struct {
	steps  int
	width  int
	height int
	m      map[coord]rune
}

func (f *floor) Print() {
	for y := 0; y < f.height; y++ {
		for x := 0; x < f.width; x++ {
			fmt.Printf("%s", string(f.m[coord{x: x, y: y}]))
		}
		fmt.Printf("\n")
	}
	fmt.Printf("\n")
}

func (f *floor) Step() bool {
	f.steps++
	movedThisStep := map[coord]struct{}{}
	toMove := map[coord]coord{}
	for y := 0; y < f.height; y++ {
		for x := 0; x < f.width; x++ {
			current := coord{x: x, y: y}
			x += 1
			if x >= f.width {
				x = 0
			}
			next := coord{x: x, y: y}
			if _, ok := movedThisStep[current]; !ok && f.m[current] == '>' && f.m[next] == '.' {
				toMove[current] = next
			}
		}
	}
	for current, next := range toMove {
		f.m[next] = f.m[current]
		f.m[current] = '.'
		movedThisStep[next] = struct{}{}
	}
	toMove = map[coord]coord{}
	for y := 0; y < f.height; y++ {
		for x := 0; x < f.width; x++ {
			current := coord{x: x, y: y}
			y += 1
			if y >= f.height {
				y = 0
			}
			next := coord{x: x, y: y}
			if _, ok := movedThisStep[current]; !ok && f.m[current] == 'v' && f.m[next] == '.' {
				toMove[current] = next
			}
		}
	}
	for current, next := range toMove {
		f.m[next] = f.m[current]
		f.m[current] = '.'
		movedThisStep[next] = struct{}{}
	}
	return len(movedThisStep) > 0
}

func partOne() {
	scanner := makeScanner(false)
	f := &floor{
		m: make(map[coord]rune),
	}
	y := 0
	for scanner.Scan() {
		line := scanner.Text()
		f.width = len(line)
		for x, v := range line {
			f.m[coord{x: x, y: y}] = v
		}
		y++
	}
	f.height = y
	for f.Step() {
	}
	fmt.Println(f.steps)
}